Civil Engineering Reference
In-Depth Information
TABLE 5-1. Elements Commonly Used in Water Engineering
Atomic
Weight
Common
Valence*
Combining
Weightâ€
Name
Symbol
Aluminum
Al
27.0
3
9.0
Arsenic
As
74.9
3
25.0
Barium
Ba
137.3
2
68.7
Boron
B
10.8
3
3.6
Bromine
Br
79.9
1
79.9
Cadmium
Cd
112.4
2
56.2
Calcium
Ca
40.1
2
20.0
Carbon
C
12.0
4
Chlorine
Cl
35.5
1
35.5
Chromium
Cr
52.0
3
6
17.3
Copper
Cu
63.5
2
31.8
Fluorine
F
19.0
1
19.0
Hydrogen
H
1.0
1
1.0
Iodine
I
126.9
1
126.9
Iron
Fe
55.8
2
3
27.9
Lead
Pb
207.2
2
103.6
Magnesium
Mg
24.3
2
12.2
Manganese
Mn
54.9
2
4
7
27.5
Mercury
Hg
200.6
2
100.3
Nickel
Ni
58.7
2
29.4
Nitrogen
N
14.0
3
5
Oxygen
O
16.0
2
8.0
Phosphorus
P
31.0
5
6.0
Potassium
K
39.1
1
39.1
Selenium
Se
79.0
6
13.1
Silicon
Si
28.1
4
6.5
Silver
Ag
107.9
1
107.9
Sodium
Na
23.0
1
23.0
Sulfur
S
32.1
2
16.0
Zinc
Zn
65.4
2
32.7
* Valence is based upon the combining value of the hydrogen atom, which is assigned the unit value of 1. The
valence of any other atom represents the number of atoms of hydrogen that will be replaced by it, or that are
equivalent to it in combining value. Thus, an atom with a valence of 2 will replace two hydrogen atoms, or
react with two hydrogen atoms. Some elements have multiple valence numbers, depending on the chemical
reaction.
†In ordinary chemical work, the atomic and combining weights are expressed as whole numbers, rather than
using a decimal place as shown in this table for fundamental reference. Thus, the atomic weight of cadmium
used in ordinary chemical work would be 112, and the combining weight would be 56.
